Interannual variations in the carbon to chlorophyll a ratios during the spring bloom in Prince William Sound, Alaska

Abstract

The carbon to chlorophyll a ratio of phytoplankton during the spring bloom in Prince William Sound, Alaska was investigated for 3 seasons and related to major physical and chemical variables. Carbon to chlorophyll a ratios (C:Chl) were determined by two methods, based on particulate organic carbon to chlorophyll (POC:Chl) and phytoplankton cell carbon to chlorophyll (PCC:Chl). These ratios were compared to a more commonly used estimate, a fixed ratio of C:Chl, taken from literature, for the spring phytoplankton community. The hypothesis that the C:Chl ratios were significantly different between years was proven false. This research indicates that the C:Chl ratio is primarily determined by species composition of the phytoplankton community rather than external factors such as nutrients, temperature or salinity. In addition, this research indicates that the identification and enumeration method, although rarely used because it is the most time and labor intensive method, provides the best estimate of phytoplankton carbon. The mean PCC:Chl ratio for all three years was 18, and is the best fixed ratio to estimate spring phytoplankton carbon in Prince William Sound when an EI Niño is not present.